diff options
author | Takashi Iwai <tiwai@suse.de> | 2015-04-28 18:11:44 +0300 |
---|---|---|
committer | Takashi Iwai <tiwai@suse.de> | 2015-04-28 18:45:45 +0300 |
commit | 1c94e65c668f44d2c69ae7e7fc268ab3268fba3e (patch) | |
tree | 14e8a5875c542973577f789d47a1f7d9419ed6fa /sound/synth/emux/emux_oss.c | |
parent | 30e5f003ff4b2be86f71733b6c9b11355d66584c (diff) | |
download | linux-1c94e65c668f44d2c69ae7e7fc268ab3268fba3e.tar.xz |
ALSA: emux: Fix mutex deadlock in OSS emulation
The OSS emulation in synth-emux helper has a potential AB/BA deadlock
at the simultaneous closing and opening:
close ->
snd_seq_release() ->
sne_seq_free_client() ->
snd_seq_delete_all_ports(): takes client->ports_mutex ->
port_delete() ->
snd_emux_unuse(): takes emux->register_mutex
open ->
snd_seq_oss_open() ->
snd_emux_open_seq_oss(): takes emux->register_mutex ->
snd_seq_event_port_attach() ->
snd_seq_create_port(): takes client->ports_mutex
This patch addresses the deadlock by reducing the rance taking
emux->register_mutex in snd_emux_open_seq_oss(). The lock is needed
for the refcount handling, so move it locally. The calls in
emux_seq.c are already with the mutex, thus they are replaced with the
version without mutex lock/unlock.
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/synth/emux/emux_oss.c')
-rw-r--r-- | sound/synth/emux/emux_oss.c | 11 |
1 files changed, 1 insertions, 10 deletions
diff --git a/sound/synth/emux/emux_oss.c b/sound/synth/emux/emux_oss.c index ab37add269ae..82e350e9501c 100644 --- a/sound/synth/emux/emux_oss.c +++ b/sound/synth/emux/emux_oss.c @@ -118,12 +118,8 @@ snd_emux_open_seq_oss(struct snd_seq_oss_arg *arg, void *closure) if (snd_BUG_ON(!arg || !emu)) return -ENXIO; - mutex_lock(&emu->register_mutex); - - if (!snd_emux_inc_count(emu)) { - mutex_unlock(&emu->register_mutex); + if (!snd_emux_inc_count(emu)) return -EFAULT; - } memset(&callback, 0, sizeof(callback)); callback.owner = THIS_MODULE; @@ -135,7 +131,6 @@ snd_emux_open_seq_oss(struct snd_seq_oss_arg *arg, void *closure) if (p == NULL) { snd_printk(KERN_ERR "can't create port\n"); snd_emux_dec_count(emu); - mutex_unlock(&emu->register_mutex); return -ENOMEM; } @@ -148,8 +143,6 @@ snd_emux_open_seq_oss(struct snd_seq_oss_arg *arg, void *closure) reset_port_mode(p, arg->seq_mode); snd_emux_reset_port(p); - - mutex_unlock(&emu->register_mutex); return 0; } @@ -195,13 +188,11 @@ snd_emux_close_seq_oss(struct snd_seq_oss_arg *arg) if (snd_BUG_ON(!emu)) return -ENXIO; - mutex_lock(&emu->register_mutex); snd_emux_sounds_off_all(p); snd_soundfont_close_check(emu->sflist, SF_CLIENT_NO(p->chset.port)); snd_seq_event_port_detach(p->chset.client, p->chset.port); snd_emux_dec_count(emu); - mutex_unlock(&emu->register_mutex); return 0; } |